hanningfield wtp
DESCRIPTION
Hanningfield WTP. Essex & Suffolk Water. UK Water Supply Only Companies. Essex Plants. Chigwell Row: 90 ML/d ozone: atmospheric pressure static mixer 18 slow sand filters (6 with GAC sandwich) 10 cm GAC on bottom Hanningfield: 220 ML/d Lever le Haye: 120 ML/d - PowerPoint PPT PresentationTRANSCRIPT
Hanningfield WTP
Essex & Suffolk Water
UK Water Supply Only Companies
Essex Plants
• Chigwell Row: 90 ML/d– ozone: atmospheric pressure static mixer– 18 slow sand filters (6 with GAC sandwich)
• 10 cm GAC on bottom
• Hanningfield: 220 ML/d• Lever le Haye: 120 ML/d
– slow sand (all sandwich) (no ozone)
• Langford: 60 ML/d– 2 stage ozone (diffusers)
• Langham: 55 ML/d– ozone: pressurized static mixer– 12 slow sand filters (10 sandwich)
Chigwell Row Plant
Langham Plant
Suffolk Plants
• Barsham– River Waverly– post GAC, no ozone
• Lound– lake source, no pesticides (no ozone)
• Ormesby– River Buer, pesticide problems– considered ozone, but ruled out in final design– 8 GAC contactors
Hanningfield Dam
• Reservoir: 25,000 ML
Essex and Hanningfield
Area
Raw Water
• DOC = 5-6 mg/L• algae
– blue greens are particularly troublesome• formerly produced high levels of THMs
– pre-chlorination
• phosphate = 2-4 mg-PO4/L
Treatment Train
• Pre ozone• Flash Mix• Pulsator Clarifier• Pellet Reactor Softener• Rapid Gravity Filter• Intermediate Ozonation• GAC Adsorption• Chlorination
Ozonation
• Liquid Oxygen Feed– owned and operated by BAA (?)
• Three Degremont Generators– 18 kg/hr each
• Dose: designed for 5 mg/L total, current application is much less– 0.75 mg/L as pre– 0.35 mg/L intermediate– no residual out of either tank– ceramic diffusers
Ozone (continued)
• Purpose– algae control– pesticide removal
• isoproturon: most importantly - works well– mecoprop, diuron, chlortoluone, 2,4-D also
• doesn’t work so well alone for atrazine or simizine– but concentrations of these are dropping anyway
– THM control
Thermal Ozone Destruct
Rapid Mix
• Original tanks were too large– floc growth began before exiting tank– Coagulant addition to tank effluent
Coagulant Addition• Addition on effluent weirAddition on effluent weir• Ferric SulfateFerric Sulfate
– 6 mg-Fe/L6 mg-Fe/L• Polymer (LT20)Polymer (LT20)
– 0.1 mg/L0.1 mg/L
Coagulation
• Removes phosphate– otherwise it would interfere with softening
process
Pulsator
• Degremont design– 3 m/hr overflow– upflow sludge blanket– draw and release on 40 s & 10 s cycle– 0.5 meter draw up
Pulsator Sludge Removal
• Sludge draw off– four hoppers– valves opened separately on a cycle
On-line Iron Analyzer
• Measures total Iron– colorimetric method
• Purpose: to monitor floc carryover– usually mirrored by
turbidity
Pumping Station
• From pulsator to softener
Lime Hoppers
Lime Saturator
Pellet Reactor Softener
• controllers
Pellet Reactor Softeners
• “Fast” alternative to precipitative softening– applicable to waters at 8 C or higher
• as temp drops below 6 C, Lime carryover occurs
– most used for groundwater• where there are now extreme low temperaturs
– only a few others for surface water• Leiden, Netherlands
• Use of sand accumulators– fine sand rises to to and stays there until it grows larger
Pellet Reactor Softeners
• Degremont Design– 8 units x 30 ML/d each– 5 minute contact (fast)– 80 m/hr overflow at center of tank
• where sludge blanket is located
• Lime addition (48 mg/L dose ?)• Introduction of Silver Sand
– 0.2 mm as clean sand– 2-3 mm after accumulation of “chalk”
Pellet Reactor Bottom
Pellet Draw-off
Pellet Reactor Softeners
• Entry of water at bottom
Top of Pellet Reactor
Pellet Reactor Softener
• overflow
Pellet Reactor Softener
• Overflow weir
Pellet Reactor Softener
• Treated water flume
Pellet Reactor Softener
• Waste sand with “chalk”
Pellet Reactor Softener
• Effluent sand
Pellet Reactor Softener
• Sand conditioning
Rapid Gravity Filters
• Anthracite/Sand• Air scour backwash
– washwater returned to reservoir
Intermediate Ozone
• Entrance security system
Intermediate Ozone
• Liquid residual monitors– all read zero!
Intermediate Ozone
• A view through the observation window• 3-chamber contactor• ability to add peroxide at 4 points for
atrazine control– not used
GAC Adsorption
• Top of contactors• Norit carbon• backwash every 12 days
– just for “good practice”
Chlorinators
• Vacuum system
Final Disinfection
• Chlorination mostly– residuals
• 0.8 mg/L at plant effluent• 0.1-0.5 at end of system
– about 50 ug/L THMs– CT standard is about 20-30 for surface water (10 for
groundwater)• company standard, none imposed by DWI
• Post contactor ammoniation (summer only)– some nitrite problems
• need occasional chlorine pulse